Proteoglycan aggregates of cartilage play critical roles within the tissue providing the mechanical resiliency vital for proper cartilage function. Degenerative diseases such as osteoarthritis lead to a loss of resiliency and damage to the cartilage itself commonly progressing to a loss of function of the afflicted joint. Successful nonsurgical intervention must provide for the appropriate biological repair which includes not only synthesis of the appropriate proteoglycan but also its appropriate incorporation into a highly organized matrix. Very little is known about these processes at present. This proposal is aimed at learning more about mechanisms utilized by chondrocytes for the synthesis and subsequent extracellular organization of proteoglycans. A newly synthesized core protein precursor is extensively modified largely through the addition of sugars, resulting in a molecule more than 10 times its original mass. During this synthetic process, a portion of the molecule must take on an appropriate conformation ultimately permitting many proteoglycan molecules, each with an associated link protein, to bind to single strands of hyaluronic acid forming aggregates. This proposal is directed at examining the process at several levels includng: 1) a determination of the sequence of events associated with the assembly of proteoglycan and link protein into aggregates, 2) a determination of the intracellular transit time for core protein, link protein and proteoglycan. 3) a characterization of a newly discovered pool of intracellular core protein which may not be converted into proteoglycan. 4) an examination of the possibility that processing of the core protein precursor into proteoglycan includes peptide cleavage, 5) an examination of the timing of addition of various monosaccharides to the core protein precursor, 6) a study of the contribution of snythesis to the heterogeneity of link protein in bovine cartilage and a comparsion of the biosynthetic process in bovine and rat cultures to determine what features might be common to both, 7) an examination on the effect of oxygen or pH on cartilage cultures with respect to the ability of newly synthesized proteoglycan to interact with hyaluronic acid. 8) examination of the location and timing of formation of disulfide bridges in the hyaluronic acid binding region of the proteoglycan.